It is our general goal to relate perception of color and brightness to underlying physiological mechanisms. This program specifically investigates the physiological mechanisms of the primate visual cortex and how groups of neurons work together to process color-contrast and luminance-contrast information. Two experimental methods are employed: (1) microelectrode recording to determine the luminance sensitivities of cortical neurons and (2) the metabolic marker 14C-2-Deoxyglucose (2-DG) for identifying the grouping and patterning of color-sensitive and luminance-sensitive cortical neurons. Building upon the results of our initial experiments using electrophysiological techniques as well as the 14C-2-DG method, we propose to: (1) Describe, by microelectrode recordings, the luminance null point for a large population of cortical neurons stimulated by drifing heterochromatic two-color grating patterns; (2) By scanning microdensitometry, describe the column density profile across the layers of visual cortex induced by color-contrast and luminance-contrast stimulation; (3) By scanning microdensitometry, examine in detail the pattern periodicity following color or luminance visual stimulation; (4) By microdensitometry, examine the cortical mosaics produced by color or luminance stimulation to determine the degree of interleaving of the neuronal aggregation; (5) Compare and contrast (2)-(4) for striate and pre-striate locations; and (6) By computer-assisted stacking of sequential autoradiography re-construct the three dimensional distribution of these stimulus dependent patterns. The general proposition tested by these experiments is that the primate visual cortex is composed of stimulus specific functional elements or columns forming a three dimensional mosaic throughout. These columns are sensitive to luminance-contrast, color-contrast, orientation, motion, etc. and have distinctively different stimulus dependent trans-laminar 2-DG uptake forms.